1. Field of the Invention
This invention relates to the flotation barrier or boom art, and, more particularly, to an improved containment barrier or boom.
2. Description of the Prior Art
The increased frequency of contamination of bodies of water such as rivers, harbors, ponds, lakes, oceans, and the like, by, for example, oil spills, has increased the need for effective containment barriers or booms wherein the area of the liquid body having the contamination may be separated from adjacent areas of the liquid body and the contamination contained within the sectioned off area. The contamination may be removed without further contamination of additional areas. Various types of booms have heretofore been utilized for providing the barrier separating the contamination area from uncontaminated areas. One type of boom that has been widely utilized is a flotation boom, generally fabricated in sections. Each section of the boom may be coupled to adjacent sections to form an entire boom of any desired length deployed in any desired geometrical configuration to contain the contamination area. Such flotation booms have generally incorporated a flotation means floating on the surface of the liquid and a dependent sinking means or skirt extending from the bottom of the flotation means into the liquid. The skirt has a predetermined depth and generally incorporates a ballast, and preferably, a tension member.
The flotation means heretofore utilized has comprised, for example, logs, sealed rigid containers such as oil drums or the like, inflatable tubular members, tubular members filled with a buoyant material, i.e., a material having a specific gravity less than 1.0, or similar devices. However, such prior art flotation means in a containment boom have generally not proven to be completely satisfactory. Since the containment boom is often stored for comparatively long periods of time and only deployed on the liquid when it is necessary to contain a contaminated area, the storage volume is preferably as small as possible. Further, since the contamination may occur quite suddenly, the boom should be able to be rapidly deployed with comparatively low drag and low turbulence inducement in the liquid. Further, it should be deployable without utilizing sophisticated machinery and/or highly skilled labor. Additionally, it is also desired that the boom be capable of articulation in both the horizontal and vertical directions, while maintaining its cross-sectional configuration, in response to the forces imposed to minimize stresses imposed on the boom as well as maintaining desired draft and freeboard and minimizing splash-over. Further, each boom section is preferably fabricated in as longitudinally long sections as possible to reduce the tubulence of mixing effect on deployment or when used, and to reduce costs associated with boom section connections.
One form of inflatable boom heretofore utilized has incorporated a plurality of boom elements, each approximately 25 yards long and has a flotation portion and a dependent skirt portion. The flotation section is a flexible fabric and has a generally rectangular configuration in the deployed condition and is transversely collapsible in the stored condition to a flat configuration in which it may, for example, be coiled. Each element is comprised of a plurality of sections on the order of 1 to 2 yards long. Each section has one or more individual spring loaded, pivotally connected rectangular frames and a check valve for admitting air into the section. In the collapsed, or storage condition, the springs allow the collapse of the rectangular frames to permit the boom to assume the transversely flat storage configuration. Means are provided, in the storage configuration, to resist the spring forces and prevent opening of the boom. On deployment, the restraints are removed and the springs force the rectangular frames into the rectangular configuration, opening the tubular member to conform to the rectangular cross-section. Air is drawn into each compartment during the opening of the tubular member through the check valve and the trapped air in the boom, which exceeds atmospheric pressure, provides buoyancy. The trapped air in the boom resists the natural liquid forces acting thereon which tend to transversely collapse the boom, and, thus, the combination of the trapped air and the spring loaded frames may be required to maintain buoyancy. On retrieval of the boom section, air must be vented by manual operation of some form of valve and each rectangular frame must be collapsed and means provided to retain the collapsed configuration. Such operating mechanical structures in the interior of the boom, the automatic opening as well as the labor associated with retrieval, have made such boom elements unsatisfactory in many applications. Such a boom is described, for example, in U.S. Pat. No. 3,798,911.
Yet another type of boom is described in U.S. Pat. No. 3,576,108, but such structure as shown therein does not readily lend itself to a comparatively small volume when such boom is in a storage condition.
Another type of boom is described in U.S. Pat. No. 3,686,869, in which a plurality of float chambers are connected to a dependent member extending below the surface of the body of liquid and in each float chamber there is provided a spring. While the boom of U.S. Pat. No. 3,686,869 may, under some circumstances be wound on a reel for storage, and then deployment therefrom, the springs in the storage condition are axially compressed against the spring constant. Further, the flotation chambers of the structure shown in U.S. Pat. No. 3,686,869 extend substantially perpendicular to the elongated longitudinal direction of the dependent skirt portion, thus adding considerable bulk, mass, and cost to such a configuration.
U.S. Pat. No. 3,811,285 shows another form of boom arrangement, in which a plurality of flotation pockets, open at the bottom, are vertically arranged in spaced relationship throughout the longitudinally elongated boom section. Within the flotation pockets, there may be provided helical springs which have a plurality of straps coupling the coils of the spring to the vertically oriented pocket on the interior thereof. Thus the axis of the helical springs are vertically oriented. While this configuration may be wound upon a reel for a storage condition, it has been found that collapsing the helical springs during the winding, because of their vertical orientation as opposed to the elongated longitudinal dimension of the boom section, presents considerable problems, since forces are not acting directly upon the spring to cause the collapse thereof into a flattened condition. That is, in winding the structure shown in U.S. Pat. No. 3,811,285 upon a reel, the forces act in a direction perpendicular to the axis of the helical coils and some additional force must be provided on the helical coils, acting in the axial direction to cause the coils to collapse to a flattened condition.
U.S. Pat. No. 4,068,478 discloses structure in which a helical member extends throughout the longitudinal direction of a tubular member, forming the flotation chamber of a containment boom section, and which is adapted to be longitudinally compressed during the storage thereof.
U.S. Pat. No. 3,803,848 discloses yet another configuration of a containment barrier or boom.
It has been found that a boom, which may be windable upon a reel during the storage thereof, and have reduced volume when so wound on the reel, but automatically expand to its desired volume upon deployment or unwinding from the reel, offers many advantages in certain applications. To achieve such automatic expansion to a full flotation condition upon deployment, it is preferred that the mechanism providing such expansion be substantially free of comparatively complex mechanical elements, and, further, that the structure should both collapse, for example, transversely, during the winding upon the reel, without utilization of any other forces to cause the collapse of the structure. Additionally, of course, the boom section should expand into its full flotation volume upon deployment from the reel, and, once again, such expansion should also be achieved without the requirement of applying any other forces except the unwinding from the reel to achieve such an expanded condition.
It has been found that when a helical spring is utilized in the flotation means, which may be a longitudinally extended tubular member, certain parameters must be followed in selecting the spring and the attachment of the spring in the flotation means in order that the helical spring will properly collapse or fold when it is wound on the reel and automatically expand to a helical configuration, thereby expanding the flotation means when it is deployed from the reel.